A Brush Stroke Synthesis Toolbox

Digital painting has progressed by leaps and bounds since its humble beginnings [30]. What some of the original painting applications called “brushes” were really simple line-drawing mechanisms based on the model of a circular tip, swept along a path. Still, within these systems, artists prevailed to make impressive images with the first inklings of a natural media style. Things have advanced greatly since then. Much of the rest of this book deals with the rise of non-photorealistic rendering, and in some cases specifically painterly rendering, in which 3D models or 2D images and videos are processed automatically to have the appearance of a piece of natural media artwork. On the other hand, traditional media artists who consider moving into the digital media world look for the same level of expressive control and manual interaction that they have mastered with physical brushes. From this perspective, painting engines that aim to replicate or emulate real artistic tools represent the path forward, and there has been a correspondingly large amount of research in the field. However, it is not the case that brush strokes are only interesting to manual digital painters. For example, in the automatic generation of painterly images from photos or 3D models, many algorithms are based around the idea of stroke-based rendering (SBR) [21], where the composition is broken down into a set of brush strokes that combine to form the target output. The primary distinction between SBR and brush simulation is that SBR assumes realistic brush strokes as an input to the algorithm, whereas brush simulation is concerned with the synthesis of those realistic brush strokes, but clearly the two areas are closely connected. SBR is discussed in detail in Chap. 1.